1. Field of the Invention
The present invention relates to a data output method and apparatus for outputting content data to be protected for copyright violation including audio data, video data for movies etc., and game program data. The present invention further relates to a data playback method and apparatus for playing back such content data, and a data recording and playback method and apparatus for recording and playing back the content data.
2. Description of the Related Art
With the recent popularity of digital content on the Internet, compact disks, digital video disks, and the like, copyright violations involving illegal duplication (copying) of such digital content are becoming problems.
Accordingly, in order to address the copyright protection problems, actions have been taken to add copyright information such as duplication-control information to digital content such that this additional information is used to prevent the content from being duplicated (copied) without permission. A noteworthy technique of preventing illegal copying is electronic watermarking which makes it difficult to tamper with the additional information.
An electronic watermark technique is a technique in which additional information is embedded as noise in a portion of video or audio data which is imperceptible to human senses, that is, which is redundant to the resulting music or image.
Additional information which has been embedded in video or audio data using the electronic watermark technique is less removed therefrom. Meanwhile, even if the additional information is embedded in video or audio data which has been filtered or compressed, the embedded additional information may be detected from that video or audio data.
Therefore, content data is transmitted, in which copyright information such as duplication generation limiting information has been embedded as the electronic watermark additional information (hereinafter referred to as “electronic watermark information”), and is used for duplication (copying) control, thereby feasibly achieving an effective copyright protection on the content data.
Digital watermark information embedded in content data is imperceptible to the human eye or ear, but may not completely affect the quality of the reproduced and output sound or the read and output images.
That is, in a conventional copyright protection method using electronic watermark information, in which electronic watermark information is embedded in content data in advance regardless of a recording (duplicating) application before being transmitted, the quality of the resulting music or image might be essentially damaged to some extent.